The toroidicity-induced Alfvén eigenmode structure in DIII-D: Implications of soft x-ray and beam-ion loss data

Carolipio, E. M.; Heidbrink, W. W.; Cheng, C. Z.; Chu, M. S.; Fu, G. Y.; Jaun, A.; Spong, D. A.; Turnbull, A. D.; White, R. B.

doi:10.1063/1.1378066

Cited by 32 publications

(28 citation statements)

References 62 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The measured frequency agrees well with the expected frequency in many devices. 32 The spatial structure is in rough qualitative agreement with theory for some modes in TFTR 33,34 but agrees rather poorly with theory in DIII-D. 35,36 There have been several notable successes of linear TAE stability theory, particularly for alpha-driven TAEs in TFTR 34 and comparisons of JET antenna measurements with calculations by the gyrokinetic PENN code. 21 The only attempt to compare theoretical predictions of fastion transport with measurements failed.…”

mentioning

confidence: 50%

“…21 The only attempt to compare theoretical predictions of fastion transport with measurements failed. 36 Despite difficulties in explaining the detailed mode structure and fast-ion transport, partial models have successfully predicted some features of nonlinear saturation, including the ''predator-prey'' model in DIII-D, 27 qualitative differences between different regimes in TFTR, 37 and ''pitch-fork'' splitting of the spectral lines in JET.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Alpha particle physics in a tokamak burning plasma experiment

Heidbrink

2002

Physics of Plasmas

Self Cite

View full text Add to dashboard Cite

Much is known about the behavior of energetic ions in tokamak devices but much remains to be understood. Single-particle effects are well understood and provide a firm basis for extrapolation to a burning plasma. In contrast, collective effects involving fast ions are more poorly understood and extrapolations are unreliable. Collective modes of concern include toroidicity-induced and ellipticity-induced Alfvén eigenmodes, kinetic ballooning modes, and internal kink modes. In addition to these magnetohydrodynamic normal modes, there are also energetic particle modes characterized by strong dependence on the fast-ion distribution function. Although many issues are important areas of study in current experiments, five issues distinguish burning plasma experiments. First, the energetic alphas are not the dominant source of free energy for the instabilities unless the fusion power exceeds the heating power by a factor of 10. Second, the damping of the instabilities depends sensitively on mode coupling to other heavily-damped waves. The magnitude of this coupling is expected to depend on the normalized thermal gyroradius, which is much smaller in a reactor. Third, in a reactor, both the radial extent of the instabilities and the fast-ion orbit contract relative to current experiments, so the fast-ion transport will change. Fourth, when instability occurs, a larger number of modes are unstable, so the mechanism of nonlinear saturation could shift from fast-ion transport to mode coupling. Fifth, because of the extreme sensitivity of energetic particle modes to the distribution function, an isotropic alpha particle distribution function differs from anisotropic fast-ion populations.

show abstract

mentioning

confidence: 50%

mentioning

confidence: 99%

Alpha particle physics in a tokamak burning plasma experiment

Heidbrink

2002

Physics of Plasmas

Self Cite

View full text Add to dashboard Cite

show abstract

“…The damage was explained qualitatively in terms of wave-particle resonances and orbital effects but no quantitative comparisons between the measured fluctuation levels and the expected transport were given in these publications. In the only quantitative comparisons between theory and experiment [5][6][7], wave amplitudes an order of magnitude larger than the measured values were needed to predict the large losses observed experimentally.…”

Section: Introductionmentioning

confidence: 99%

Central flattening of the fast-ion profile in reversed-shear DIII-D discharges

et al. 2008

View full text Add to dashboard Cite

Neutral beam injection into a plasma with negative central shear produces a rich spectrum of toroidicity-induced and reversed-shear Alfvén eigenmodes in the DIII-D tokamak. The application of fast-ion D α (FIDA) spectroscopy shows that the central fast-ion profile is flattened in the inner half of the discharge. Neutron and equilibrium measurements corroborate the FIDA data. The temporal evolution of the current profile is also strongly modified. Studies in similar discharges show that flattening of the profile correlates with the mode amplitude and that both types of Alfvén modes correlate with fast-ion transport. Calculations by the ORBIT code do not explain the observed fast-ion transport for the measured mode amplitudes, however. Possible explanations for the discrepancy are considered.

show abstract

“…While a number of mechanisms for accelerated transport of fast ions in the presence of a perturbation field have been identified and are well established theoretically, there have been relatively few quantitative comparisons of experimental measurements with theory. For the case of Alfven Eigenmodes (AEs) [3][4][5][6], quantitative comparisons between the measured fluctuation levels and the expected transport were first presented in [7,8] and more recently and with state of the the art diagnostics in [9]. In all three cases it was found that calculations with measured mode amplitudes significantly underestimate the observed fast ion transport and that a reasonable match was only reached after increasing the mode amplitude artificially by an order of magnitude.…”

Section: Introductionmentioning

confidence: 99%

Study of fast-ion transport induced by fishbones on JET

Thun

Salmi²,

Perona

et al. 2012

Nucl. Fusion

View full text Add to dashboard Cite

Abstract. The impact of fishbone oscillations onto a confined fast ion population is simulated for a JET plasma and benchmarked against experiment quantitatively with the help of neutron rate measurements. The transient drops in volume integrated neutron emission are found to be mainly caused by the spatial redistribution of the (neutral beam injected) fast ion population confined in the plasma rather than by fast ion loss. The simulations yield a quadratic dependence of the neutron drop on the fishbone amplitude.It is found that the simulations are able to correctly reproduce the magnitude of the experimentally observed drop in volume integrated neutron emission to within a factor 2. Furthermore, frequency chirping is found to be important. Omitting the fishbone frequency chirp in the simulations reduces the magnitude of the neutron rate drop (and hence fast ion redistribution) to about half its original value.

show abstract

The toroidicity-induced Alfvén eigenmode structure in DIII-D: Implications of soft x-ray and beam-ion loss data

Cited by 32 publications

References 62 publications

Alpha particle physics in a tokamak burning plasma experiment

Alpha particle physics in a tokamak burning plasma experiment

Central flattening of the fast-ion profile in reversed-shear DIII-D discharges

Study of fast-ion transport induced by fishbones on JET

Contact Info

Product

Resources

About